1. Field of the Invention
The present invention relates generally to tools and equipment used in the oil, gas, and water well industry, and more specifically to a treatment tool which secures in line along the pump actuation or "sucker" rod string in a completed well hole. The treatment tool provides for the distribution and pressure regulation of a solvent or other fluid, which is pumped into the hole through the sucker rod for distribution into the production tube or pipe string. The device may be used to provide a continuous supply of solvent or other fluid to the oil or other fluid being pumped or delivered from the well, while the well remains in continuous operation.
2. Description of the Related Art
Wells drilled in the ground for the drawing of subterranean fluid substances, often encounter various problems with undesirable foreign matter which at least partially blocks the production tube or pipe string of the finished well and obstructs the pumping or flow of the fluid from the well. When this occurs, additional time and expense is encountered as the foreign material is removed from the well and fluid flow resumes.
This is particularly true in the oil industry, where subterranean crude oil deposits generally have less desirable substances mixed therein. One of these substances is called paraffin, a hydrocarbon which hardens to form a wax-like material as it cools. While the crude oil is universally quite warm or even hot at a depth from a few thousand to several thousand feet beneath the surface, it tends to cool as it rises up the production tube string of a producing well. When the paraffin rises to a depth where the ambient temperature is around 160 degrees Fahrenheit, it begins to solidify and adhere to the walls of the production tube string. The problem becomes worse with decreasing temperatures nearer the surface.
The solidifying paraffin will eventually block the oil flow from below, and require treatment of the production string in order to remove the paraffin buildup. This is conventionally done by mechanical means, electrical heating, hot water, and/or solvents introduced into the well. However, the various means of removing the paraffin from the production string generally require that flow from the well (either pumped or free flowing) be stopped while the treatment means is introduced into the well, and the well is treated. For example, chemical treatment using solvents is quite commonly used to remove paraffin buildup, but the chemicals are conventionally forced down the production string, in the opposite direction of pumped or natural flow. Obviously, oil cannot be recovered from the well during the time the chemical is being introduced into the well.
However, even if the paraffin buildup is removed from the production string, paraffin buildup may still occur in the oil processing and storage system after it leaves the well. Anywhere the temperature drops below the critical level of about 160 degrees Fahrenheit, paraffin will begin to harden in the system. Typically, oil leaves the well head to a tank battery, or series of storage tanks. The oil is then processed to remove water and gas mixed therewith, by heating in a heater treater. Paraffin makes it difficult to separate water from the oil, thus requiring additional heat (generally in the form of gas separated from the oil) to produce the desired reaction. Moreover, even if the paraffin is heated to melting in the heater treater, it will still solidify in valves, pipelines, and storage tanks prior to reaching the heater.
Accordingly, a need will be seen for a means of treating a producing well to remove foreign substances therefrom on a continuous basis, without interrupting the output of the well. The foreign substance removal means is particularly needed in the case of wells for oil with paraffin mixed therewith, to dissolve the paraffin and keep it in solution in the oil from a point in the well below the temperature at which it begins to solidify, and throughout the entire pipe and tank system of the oil field. While the present invention is particularly well suited for use in the oil production industry, it may also be adapted for use with other types of subterranean wells. A discussion of the related art of which the inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,011,906 issued on Mar. 15, 1977 to Harvey C. Alexander et al. describes a Downhole Valve For Paraffin Control, comprising a non-concentric (axially offset) valve which is assembled as a "sub" or short length of the production tube string. Solvent is forced down the production string to the valve, where a ball check valve is forced from its normally closed position by the pressure of the solvent, to allow the solvent to flow outwardly from the production string to the space between the production string and casing. It will be seen that the forcing of the solvent downwardly through the production string, which is normally used to deliver oil to the surface, requires that the well be shut down during the time that the solvent is being forced into the well. The present valve tool, adapted for inclusion as a "sub" in the sucker rod of the well, allows oil (or other substance being delivered by the well) to continue to flow upwardly through the production tube string without interruption, during treatment of the well. The solvent is carried up through the production tube with the flow of fluid being delivered from the bottom of the well, to flush paraffin or other substances from the production string.
U.S. Pat. No. 4,224,993 issued on Sep. 30, 1980 to Leonard Huckaby describes a Dewaxing Valve For Use In Oil Wells, comprising a valve mounted externally to the production tube, between the production string and the outer casing of the downhole. While the valve mechanism is somewhat different than that of the Alexander et al. valve discussed above, the operation is similar, with the well being shut down during the treatment process.
U.S. Pat. No. 4,279,306 issued on Jul. 21, 1981 to Robert D. Weitz describes a Well Washing Tool And Method, comprising a plurality of resilient packings on a "sub" which secures in line with the production tube string of the well. Pressure causes the central sleeves of the device to extend, thereby compressing the packings against the inner walls of the well casing. Sealing the device against the well casing routes the washing fluid through the perforated casing to wash any loose material away which may surround the outer casing. The fluid returns to the annulus between the casing and production tubing by perforations in the casing above the tool. Again, the well cannot produce oil or other fluid during use of the Weitz tool, as fluid under pressure is being forced downwardly through the production tube string, unlike the present invention where downward fluid flow is only through the hollow sucker rod.
U.S. Pat. No. 4,681,167 issued on Jul. 21, 1987 to Paul B. Soderberg describes an Apparatus And Method For Automatically And Periodically Introducing A Fluid Into A Producing Oil Well. The apparatus includes a valve placed in the downhole, which valve is actuated by pressure and/or movement of the sucker rod therethrough. The valve essentially fills the inside of the production tube string, with actuation either blocking or opening the valve to prevent or allow fluid to flow through the production string. The device operates generally in the manner described above for the other systems of the related art, in that fluid must be pumped downwardly through the production string from time to time in order to flush paraffin or other substances from the production tube string. This of course requires that fluid production from the well be stopped during the time that solvents or other fluids are being forced down the production tube string. While Soderberg states that "Present methods for removing such deposits employ hot oil, water or steam which is generally forced down the annulus between the production string and borehole casing" (column 1, lines 44-47), none of the related art discussed above, including Soderberg, do so. Rather, they force the fluid down the production tube string, rather than down the annulus between the production string and casing or wall of the downhole.
U.S. Pat. No. 4,995,462 issued on Feb. 26, 1991 to David Sask et al. describes a Dewaxing Control Apparatus For Oil Well, comprising a housing installed in line with the production tubing, as in the case of other devices discussed above. Dewaxing solvent or the like is pumped down the annulus between the well casing or wall and the production tubing, with the device blocking further downward flow therepast. The solvent then enters the interior of the production tube string by means of passages through the device, and is flushed back to the surface by means of the upward flow of oil through the interior of the production tube string. This is the only art of that discussed above, which causes the solvent to flow upwardly through the production string, in the manner of the present invention. However, Sask et al. still do not pump the fluid downwardly through the hollow sucker rod, or provide a valve which is installed in the sucker rod rather than the production tube string, as in the present invention. If the Sask et al. valve required removal from the hole, the production tube string would have to be lifted and disassembled at least to the depth of the valve. Such production tube removal would of course also require the removal of the entire sucker rod string before removal of the production tube string could take place. In the present invention, only the sucker rod string would have to be removed from the hole, with the production tube string remaining in place in the hole.
U.S. Pat. No. 5,056,599 issued on Oct. 15, 1991 to Walter B. Comeaux et al. describes a Method For Treatment Of Wells, comprising a telescoping valve which is axially offset from the production tube string, in a configuration somewhat similar to the device of the patent to Huckaby described further above. Comeaux et al. provide an initial balancing pressure in their valve by means of a compressed nitrogen charge, which holds the valve in a closed position until a superior pressure in the well downhole pushes the valve open. The Comeaux valve depends upon pneumatic means and differential pressure for operation, unlike the present well treatment tool, and also requires that production flow from the well be interrupted for the treatment fluid (hot water, solvent, etc.) to be introduced down the production tube string, where the Comeaux et al. valve routes it into the well casing. The present valve routes the solvent down the hollow interior of the sucker rod, where the valve is disposed, and routes the fluid outwardly from the sucker rod into the production tube interior.
U.S. Pat. No. 5,282,263 issued on Jan. 25, 1994 to John E. Nenniger describes a Method Of Stimulating Oil Wells By Pumped Solvent Heated In Situ To Reduce Wax Obstructions. The apparatus used in the method is an electrical resistance heater which is lowered to the bottom of the production tube string of the well. Solvent is then introduced into the well via the production tube string, and heated by the heater. As in all but one of the prior art devices discussed above, production must be stopped when the Nenniger method and apparatus is used in order for the solvent to be pumped into the well, downwardly through the production tube string. Moreover, the Nenniger apparatus and method circulates the solvent outwardly through the conventional passages in the lower end of the production tube string and casing, and into the surrounding geological structure. The Nenniger heater element also precludes the installation of a pump in the well, as it seals against the pump seating nipple at the bottom of the production tube string and takes the position of the pump. Thus, production must be suspended in a pumping well, with the pump and sucker rod removed for installation of the Nenniger apparatus.
Finally, PCT Patent Publication W092/06274 published on Apr. 16, 1992 to John E. Nenniger describes a Method And Apparatus For Well Stimulation. This patent publication corresponds to the U.S. patent to the same inventor, described immediately above, with the same differences and distinctions being noted.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.